An ordered lipid membrane useful as a chemoreceptive transducer in an electrochemical cell is known, as illustrated by U.S. Pat. Nos. 4,661,235 and 4,637,861, both to Krull and Thompson. Such membranes are modified to include a complexing agent for selectively interacting with a particular analyte of interest. However, a drawback is that these membranes may also interact non-selectively by adsorption/absorption of various species, with resultant undesirable transmembrane current perturbation. Furthermore, exposure of a membrane surface to a sample solution permits membrane damage and unwanted solution convection effects.
Krull et al, Abstract 11-2, 67th Annual CIC Conference (June 1984) disclose advances in Langmuir-Blodgett thin-film deposition technology for providing substrate-stabilized, lipid membrane structures. This abstract mentions techniques for such deposition, including schemes involving gel protection.
Heckmann et al, Thin Solid Films, 99: 265 (1983) describe a hyperfiltration membrane. It is an object of this work to produce an active layer on top of a membrane for ion permeability control, thereby providing a decreased electrolyte retention capacity with resultant increased water permeability, compared to conventional membranes. The hyperfiltration membrane is a cross-linked monolayer, prepared by cross-linking surfactants having glucose hydrophilic head groups with epichlorohydrin. To extend the selective permeability of the membrane into the range of molecules of medium size, the incorporation of hydrophobic ionophores and pore molecules into the membrane is proposed.
As illustrated by Thompson et al, Talanta, 30: 919 (1983), a gas sensor cell that includes a Teflon.TM. semipermeable membrane and a bilayer lipid membrane, modified to be selective for ammonium ion, is known. FIG. 5 of this publication depicts calculated values for a hypothetical cell formed by removal of the Teflon membrane, and replacement of the aqueous phase with a hydrated gel-like layer.
To prevent membrane damage and undesirable solution convection effects, there is a need for a protected, lipid membrane-based device useful as a chemoreceptive transducer. The discovery of such a device would constitute an even greater contribution to the art if it could also be used to enhance selectivity by preventing interfering chemical species from reaching the lipid membrane surface. Also needed is an improved lipid membrane-based gas sensor. Such devices would beneficially make possible improved processes for analysis.